Sensors

Research

13 pages, 9099 KiB

Open AccessArticle

Improving the Performance of Pseudo-Random Single-Photon Counting Ranging Lidar

by Yang Yu, Bo Liu and Zhen Chen

Sensors 2019, 19(16), 3620; https://doi.org/10.3390/s19163620 - 20 Aug 2019

Cited by 17 | Viewed by 3928

A new encoding method is proposed to improve the performance of pseudo-random single-photon counting ranging (PSPCR) Lidar. The encoding principle and methodology are presented. In addition, the influence of detector’s dead time on the detection probability is analyzed with theoretical derivation and Monte [...] Read more.

A new encoding method is proposed to improve the performance of pseudo-random single-photon counting ranging (PSPCR) Lidar. The encoding principle and methodology are presented. In addition, the influence of detector’s dead time on the detection probability is analyzed with theoretical derivation and Monte Carlo simulation. Meanwhile, we propose using macro code as the analysis unit to quantitatively analyze the detection probability and single-photon detection efficiency of the traditional PSPCR Lidar and the modulated PSPCR Lidar. The Monte Carlo simulation and experiment prove that the proposed method exhibited better ranging performance than the traditional PSPCR Lidar system. Full article

(This article belongs to the Special Issue Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing)

► Show Figures

Figure 1

14 pages, 4199 KiB

Open AccessArticle

Carrier-to-Noise-Threshold Filtering on Off-Shore Wind Lidar Measurements

by Sven-Erik Gryning and Rogier Floors

Sensors 2019, 19(3), 592; https://doi.org/10.3390/s19030592 - 30 Jan 2019

Cited by 18 | Viewed by 5475

Abstract

Wind lidar observations are characterized by a Carrier-to-Noise-Ratio that is often used to filter the observations. The choice of the Carrier-to-Noise-Ratio threshold value for the wind lidar observations is found to have an effect on the climatological wind speed distribution in such a [...] Read more.

Wind lidar observations are characterized by a Carrier-to-Noise-Ratio that is often used to filter the observations. The choice of the Carrier-to-Noise-Ratio threshold value for the wind lidar observations is found to have an effect on the climatological wind speed distribution in such a way that when the Carrier-to-Noise-Ratio (CNR) threshold value is increased the wind speed distribution is shifted to higher values. Based on one year of observations carried out with a wind lidar from 126 m to 626 m height at the FINO3 (Forschungsplattform in Nord- und Ostsee Nr. 3) research platform in the North Sea, the effect that the choice of the Carrier-to-Noise threshold value has on the climatology of the wind speed and direction as well as the wind power density in relation to wind energy is illustrated and discussed. In the one-year data set considered here it is found that for thresholds larger than −29 dB, the mean wind speed and wind rose measured by the wind lidar become a function of the threshold value, and for values smaller than ~ −29 dB further decrease of the Carrier-to-Noise-Ratio threshold has a minor effect on the estimated mean wind speed and wind rose. The analysis of the data set from the North Sea shows that the limit for the Carrier-to-Noise-Ratio of the observations should be −29 dB or less to obtain a threshold independent estimate of the mean wind speed and wind rose. Alternatively, all valid observations should be used for the analysis. Although this study is specific for the conditions in the North Sea, we suggest that for a representative estimation of the wind resource with wind lidars, the effect of the CNR threshold filtering on the wind distribution should be studied when the recovery rate is less than 100%. Full article

(This article belongs to the Special Issue Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing)

► Show Figures

Figure 1

13 pages, 4460 KiB

Open AccessArticle

LED Mini Lidar for Atmospheric Application

by Tatsuo Shiina

Sensors 2019, 19(3), 569; https://doi.org/10.3390/s19030569 - 29 Jan 2019

Cited by 21 | Viewed by 6555

Abstract

The creation of a compact and easy-to-use atmospheric lidar has been the aim of researchers for a long time. Micro Pulse Lidars (MPL) and commercialized ceilometers were designed for such purposes. Laser Diodes (LD) and Diode-Pumped Solid State (DPSS) Laser technology has evolved, [...] Read more.

The creation of a compact and easy-to-use atmospheric lidar has been the aim of researchers for a long time. Micro Pulse Lidars (MPL) and commercialized ceilometers were designed for such purposes. Laser Diodes (LD) and Diode-Pumped Solid State (DPSS) Laser technology has evolved, making lidar system more compact; however, their vulnerability to static electricity and fluctuation of electrical power prevented the growth of atmospheric lidar technology as a system suited to all kinds of users. In this study, a mini lidar with a Light Emitting Diode (LED)-based light source was designed and developed. As LED lamp modules do not need a heat sink or fan, they are resilient and can emit light for long periods with constant intensity. They also offer ease of handling for non-professionals. On the other hand, a LED lamp module has a large divergence, when compared to laser beams. A prototype LED mini lidar was thus developed, with focus on transmitting power optimization and optical design. This low-cost lidar system is not only compact, but also offers near-range measurement applications. It visualizes rapid activities of small air cells in a close range (surface atmosphere), and can verify and predict the condition of the surface atmosphere. This paper summarizes the principle, design, practical use and applications of the LED mini-lidar. Full article

(This article belongs to the Special Issue Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing)

► Show Figures

Figure 1

14 pages, 3904 KiB

Open AccessArticle

Validation of an Airborne Doppler Wind Lidar in Tropical Cyclones

by Lisa R. Bucci, Christopher O’Handley, G. David Emmitt, Jun A. Zhang, Kelly Ryan and Robert Atlas

Sensors 2018, 18(12), 4288; https://doi.org/10.3390/s18124288 - 5 Dec 2018

Cited by 26 | Viewed by 4041

Abstract

This study presents wind observations from an airborne Doppler Wind Lidar (ADWL) in 2016 tropical cyclones (TC). A description of ADWL measurement collection and quality control methods is introduced for the use in a TC environment. Validation against different instrumentation on-board the National [...] Read more.

This study presents wind observations from an airborne Doppler Wind Lidar (ADWL) in 2016 tropical cyclones (TC). A description of ADWL measurement collection and quality control methods is introduced for the use in a TC environment. Validation against different instrumentation on-board the National Oceanographic and Atmospheric Administration’s WP-3D aircraft shows good agreement of the retrieved ADWL measured wind speed and direction. Measurements taken from instruments such as the global positioning system dropsonde, flight-level wind probe, tail Doppler radar, and Stepped Frequency Microwave Radiometer are compared to ADWL observations by creating paired datasets. These paired observations represent independent measurements of the same observation space through a variety of mapping techniques that account for differences in measurement procedure. Despite high correlation values, outliers are identified and discussed in detail. The errors between paired observations appear to be caused by differences in the ability to capture various length scales, which directly relate to certain regions in a TC regime. In validating these datasets and providing evidence that shows the mitigation of gaps in 3-dimensional wind representation, the unique wind observations collected via ADWL have significant potential to impact numerical weather prediction of TCs. Full article

(This article belongs to the Special Issue Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing)

► Show Figures

Figure 1

11 pages, 3591 KiB

Open AccessArticle

A Hardware Implemented Autocorrelation Technique for Estimating Power Spectral Density for Processing Signals from a Doppler Wind Lidar System

by Sameh Abdelazim, David Santoro, Mark Arend, Fred Moshary and Sam Ahmed

Sensors 2018, 18(12), 4170; https://doi.org/10.3390/s18124170 - 28 Nov 2018

Cited by 6 | Viewed by 4235

Abstract

A signal processing technique utilizing autocorrelation of backscattered signals was designed and implemented in a 1.5 µm all-fiber wind sensing Coherent Doppler Lidar (CDL) system to preprocess atmospheric signals. The signal processing algorithm’s design and implementation are presented. The system employs a 20 [...] Read more.

A signal processing technique utilizing autocorrelation of backscattered signals was designed and implemented in a 1.5 µm all-fiber wind sensing Coherent Doppler Lidar (CDL) system to preprocess atmospheric signals. The signal processing algorithm’s design and implementation are presented. The system employs a 20 kHz pulse repetition frequency (PRF) transmitter and samples the return signals at 400 MHz. The logic design of the autocorrelation algorithm was developed and programmed into a field programmable gate array (FPGA) located on a data acquisition board. The design generates and accumulates real time correlograms representing average autocorrelations of the Doppler shifted echo from a series of adjustable range gates. Accumulated correlograms are streamed to a host computer for subsequent processing to yield a line of sight wind velocity. Wind velocity estimates can be obtained under nominal aerosol loading and nominal atmospheric turbulence conditions for ranges up to 3 km. Full article

(This article belongs to the Special Issue Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing)

► Show Figures

Figure 1

9 pages, 2158 KiB

Open AccessArticle

Comparison of CO₂ Vertical Profiles in the Lower Troposphere between 1.6 µm Differential Absorption Lidar and Aircraft Measurements Over Tsukuba

by Yasukuni Shibata, Chikao Nagasawa, Makoto Abo, Makoto Inoue, Isamu Morino and Osamu Uchino

Sensors 2018, 18(11), 4064; https://doi.org/10.3390/s18114064 - 21 Nov 2018

Cited by 7 | Viewed by 5604

Abstract

A 1.6 μm differential absorption Lidar (DIAL) system for measurement of vertical CO₂ mixing ratio profiles has been developed. A comparison of CO₂ vertical profiles measured by the DIAL system and an aircraft in situ sensor in January 2014 over the [...] Read more.

A 1.6 μm differential absorption Lidar (DIAL) system for measurement of vertical CO₂ mixing ratio profiles has been developed. A comparison of CO₂ vertical profiles measured by the DIAL system and an aircraft in situ sensor in January 2014 over the National Institute for Environmental Studies (NIES) in Tsukuba, Japan, is presented. The DIAL measurement was obtained at an altitude range of between 1.56 and 3.60 km with a vertical resolution of 236 m (below 3 km) and 590 m (above 3 km) at an average error of 1.93 ppm. An in situ sensor for cavity ring-down spectroscopy of CO₂ was installed in an aircraft. CO₂ mixing ratio measured by DIAL and the aircraft sensor ranged from 398.73 to 401.36 ppm and from 399.08 to 401.83 ppm, respectively, with an average difference of −0.94 ± 1.91 ppm below 3 km and −0.70 ± 1.98 ppm above 3 km between the two measurements. Full article

(This article belongs to the Special Issue Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing)

► Show Figures

Figure 1

19 pages, 4780 KiB

Open AccessArticle

Improvement of CO₂-DIAL Signal-to-Noise Ratio Using Lifting Wavelet Transform

by Chengzhi Xiang, Ge Han, Yuxin Zheng, Xin Ma and Wei Gong

Sensors 2018, 18(7), 2362; https://doi.org/10.3390/s18072362 - 20 Jul 2018

Cited by 7 | Viewed by 3693

Abstract

Atmospheric CO₂ plays an important role in controlling climate change and its effect on the carbon cycle. However, detailed information on the dynamics of CO₂ vertical mixing remains lacking, which hinders the accurate understanding of certain key features of the carbon [...] Read more.

Atmospheric CO₂ plays an important role in controlling climate change and its effect on the carbon cycle. However, detailed information on the dynamics of CO₂ vertical mixing remains lacking, which hinders the accurate understanding of certain key features of the carbon cycle. Differential absorption lidar (DIAL) is a promising technology for CO₂ detection due to its characteristics of high precision, high time resolution, and high spatial resolution. Ground-based CO₂-DIAL can provide the continuous observations of the vertical profile of CO₂ concentration, which can be highly significant to gaining deeper insights into the rectification effect of CO₂, the ratio of respiration photosynthesis, and the CO₂ dome in urban areas. A set of ground-based CO₂-DIAL systems were developed by our team and highly accurate long-term laboratory experiments were conducted. Nonetheless, the performance suffered from low signal-to-noise ratio (SNR) in field explorations because of decreasing aerosol concentrations with increasing altitude and surrounding interference according to the results of our experiments in Wuhan and Huainan. The concentration of atmospheric CO₂ is derived from the difference of signals between on-line and off-line wavelengths; thus, low SNR will cause the superimposition of the final inversion error. In such a situation, an efficient and accurate denoising algorithm is critical for a ground-based CO₂-DIAL system, particularly in field experiments. In this study, a method based on lifting wavelet transform (LWT) for CO₂-DIAL signal denoising was proposed. This method, which is an improvement of the traditional wavelet transform, can select different predictive and update functions according to the characteristics of lidar signals, thereby making it suitable for the signal denoising of CO₂-DIAL. Experiment analyses were conducted to evaluate the denoising effect of LWT. For comparison, ensemble empirical mode decomposition denoising was also performed on the same lidar signal. In addition, this study calculated the coefficient of variation (CV) at the same altitude among multiple original signals within 10 min and then performed the same calculation on the denoised signal. Finally, high-quality signal of ground-based CO₂-DIAL was obtained using the LWT denoising method. The differential absorption optical depths of the denoised signals obtained via LWT were calculated, and the profile distribution information of CO₂ concentration was acquired during field detection by using our developed CO₂-DIAL systems. Full article

(This article belongs to the Special Issue Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing)

► Show Figures

Figure 1

12 pages, 4623 KiB

Open AccessArticle

Atmospheric Pollution Monitoring in Urban Area by Employing a 450-nm Lidar System

by Zheng Kong, Zhi Liu, Lishan Zhang, Peng Guan, Limei Li and Liang Mei

Sensors 2018, 18(6), 1880; https://doi.org/10.3390/s18061880 - 8 Jun 2018

Cited by 24 | Viewed by 6653

Abstract

In past decades, lidar techniques have become main tools for atmospheric remote sensing. However, traditional pulsed lidar systems are relatively expensive and require considerable maintenance. These shortcomings may be overcome by the development of a blue band Scheimpflug lidar system in Dalian, Northern [...] Read more.

In past decades, lidar techniques have become main tools for atmospheric remote sensing. However, traditional pulsed lidar systems are relatively expensive and require considerable maintenance. These shortcomings may be overcome by the development of a blue band Scheimpflug lidar system in Dalian, Northern China. Atmospheric remote measurements were carried out for 10 days in an urban area to validate the feasibility and performance of a 450-nm Scheimpflug lidar system. A 24-h continuous measurement was achieved in winter on a near horizontal path with an elevation angle of about 6.4°. The aerosol extinction coefficient retrieved by the Fernald-inversion algorithm shows good agreement with the variation of PM10/PM2.5 concentrations recorded by a national pollution monitoring station. The experimental result reveals that the linear ratio between the aerosol extinction coefficient and the PM10 concentration under high relative humidity (75–90%) is about two-times that in low relative humidity (≤75%) when the PM10 concentrations are less than 100 µg/m³. Full article

(This article belongs to the Special Issue Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (8 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI